1. Field of the Invention
This invention relates generally to a compact conductor device which includes a plurality of conductors extending in parallel and spaced apart relationship with respect to one another, each conductor being supported by a pair of insulators spaced apart from one another along the longitudinal direction of the conductor, and an insulating member positioned along the lengths of the conductors between the support points of each of the conductors for maintaining the conductors in spaced apart relationship between the insulators.
2. Description of the Prior Art
First, a conductor device and an insulating member used in a metal-enclosed switchgear will be explained as an example. FIG. 1 shows a typical construction of a three phase three wipe type metal-enclosed switchgear. In FIG. 1, numeral 1 designates an enclosure, the internal space of which is separated, depending upon the type of the enclosure, by plates 30 into an equipment compartment 2, a power source compartment 3 and a load compartment 4. On the front side of the equipment compartment 2 and the power source compartment 3, doors 5 are provided. Numeral 6 designates a conductor device which includes three conductors 21 supported by insulators 16 such as epoxy insulators. Numerals 6A and numerals 7 (only one being shown) designate three branch conductors. Three current transformers 8 (only one being shown) are connected intermediately of the three branch conductors 7, respectively. A circuit breaker 11 with three circuit breaking portions (not shown) is encased in the equipment compartment 2. Three upper disconnecting devices 12 (only one being shown) are provided in the separating plate 30 between the equipment compartment 2 and the power source compartment 3.
Three lower disconnecting devices 13 (only one being shown) are provided in the separating plate 30 between the equipment compartment 2 and the load compartment 4. One end of each of the branch conductors 6A is connected to an individual conductor 21. Each other end of the branch conductors 6A is connected through the individual upper disconnecting device 12 to an individual first terminal of the circuit breaker 11. One end of each of the branch conductors 7 is connected through the individual lower disconnecting device 13 to an individual second terminal of the circuit breaker 11. Each other end of the branch conductors 7 is connected through an individual cable head 9 (only one being shown) to an individual load cable 10 (only one being shown).
From the viewpoint of economy, it is advantageous to reduce the size of the metal-enclosed switchgear. For this purpose, the reduction of spaces between the conductors constituting the main circuit of the switchgear is most effective.
FIGS. 2a, 2b and 2c show the conductor device 6 in the metal-enclosed switchgear shown in FIG. 1 in more detail. In the case of a three-phase power line, for example, three conductors 21 are extended in parallel so that the longer side in cross section of each rectangular conductor is disposed vertically in order to reduce the interphase distance A. For reinforcing the conductors 21, an insulating plate 20 having supporting grooves is provided. An intermediate portion of each conductor 21 between the insulators 16 is supported in the groove of the insulating plate 20 so that any plastic deformation of a conductor 21 caused by the electromagnetic force is thereby prevented. The intermediate portion of each conductor 21 may be supported tightly or loosely with tiny gaps in the groove of the insulating plate 20 depending on how to assemble the conductor device.
In this case, however, where it is assumed that the distance from the conductor 21 to ground along the surface of an insulator 16 is L, the distance M between two adjacent conductors 21 along the surface of the insulating plate 20 is expressed as follows, because of the difference between the phase voltage and the interphase voltage: EQU M=.sqroot.3.multidot.L
The creeping distance M is required for preventing power failure regardless of deposition of dirt or collection of humidity on the insulating plate 20, and maintaining the relation of M=.sqroot.3.multidot.L is essential from the viewpoint of insulation coordination. In other words, the interphase distance A between the conductors 21 supported by the insulating plate 20 cannot be reduced less than the height B of the insulator 16 under the prior art. Of course, the height B of the insulator 16 is so selected that the aforementioned creeping distance L can be effectively provided.
Since the creeping distance M larger than .sqroot.3 times the distance L from the conductor to ground along the surface of the insulator must be maintained under the prior art between the conductors 21 supported against the interphase voltages, there is a limitation in reducing the interphase distance A. As a result, the size of the switchgear cannot be economized regardless of the limitation under the prior art.